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Avian botulism kills 67 birds on Maui, claims over 300 birds on Kauai earlier in the year


Multiple actions urged to stop spread among native, migratory waterbirds

HONOLULU — Wetland biologists and others involved in managing lands with associated wetlands have been notified by the Department of Land and Natural Resources’ Division of Forestry and Wildlife (DOFAW) of a recent avian botulism outbreak affecting waterbirds on Maui. In just over a week, 67 birds have been found dead at Kanaha Pond Wildlife Sanctuary in Kahului including Hawaiian Stilt, Hawaiian Coot, and Hawaiian Ducks of adult and juvenile stages. The paralytic disease has killed adult birds on their nests, also causing the eggs to be lost.

Because botulinum toxin can be produced in most wetlands, and transported to new wetlands by dead or dying waterfowl, landowners and managers, both public and private, are being asked to frequently survey their wetlands for sick and/or dead birds, remove any dead or dying birds from the wetland, and contact local DOFAW biologists for guidance.

Earlier this year a botulism outbreak in Hanalei, Kauai resulted in over 300 sick and dead birds being collected by USFWS refuge staff. Additionally, numerous other botulism fatalities have also been reported at wetlands throughout the state.

Botulism is a paralytic condition brought on by the consumption of a naturally occurring toxin produced by the bacterium Clostridium botulinum. It is an intoxication rather than an infectious disease. Botulism, type C is commonly found in Hawaiian soils and is NOT dangerous to humans. Particular environmental conditions in wetlands will sometimes allow this bacterium to produce botulinum toxin; the toxin is then accumulated in aquatic invertebrates. It is consumption of these toxic invertebrates by waterfowl that leads to mortality.

In Hawai‘i, birds commonly affected include waterfowl frequenting wetlands such as our endangered Hawaiian coots, Hawaiian ducks, Laysan ducks, Hawaiian moorhen, Hawaiian stilts, Black-crowned night- herons, and various migratory waterfowl and shorebirds.

The U.S. Geological Survey (USGS) National Wildlife Health Center Honolulu Field Station (NWHC-HFS) has been working closely with the US Fish and Wildlife Service and the State of Hawaii DLNR to investigate and confirm botulism as a cause of waterfowl mortality in Hanalei and Kahului. The NWHC-HFS provides technical assistance to federal, state, municipal, and non-governmental organizations on wildlife health related matters in Hawai‘i and the Pacific.

“Part of our role is to determine the cause of death during unusual wildlife mortality events involving native and endangered species and provide management recommendations to address and mitigate such mortalities” said Dr. Thierry Work, Wildlife Disease Specialist for the USGS National Wildlife Health Center Honolulu Field Station. “For this particular event, our team first conducts necropsies of freshly dead birds here in Honolulu and then sends samples to the National Wildlife Health Center in Madison Wisconsin for confirmation of botulism.”


Botulism is a natural toxin produced by a bacterium (Clostridium botulinum) commonly found in the soil. There are several types of botulism toxin some of which can affect humans who eat improperly canned foods. Birds have their own kind of botulism (Type C in Hawai‘i) that does not affect humans. When anaerobic conditions occur in water (low or no oxygen content) botulism type C is concentrated in aquatic invertebrates that filter feed sediments or water. When birds eat the invertebrates, they get a concentrated package of toxin. A bird-to-bird cycle can also exist where maggots feeding on dead birds can concentrate the toxin and can then be eaten by and poison other birds.

Avian botulism most often affects waterfowl. Typical clinical signs in birds with botulism include weakness, lethargy, and inability to hold up the head or to fly. For waterfowl, this can be catastrophic because inability to hold up the head leads to drowning.

In Hawai‘i, birds commonly affected include endangered Hawaiian ducks, Laysan ducks, Hawaiian coots, Hawaiian moorhens, and Hawaiian stilts. Black-crowned night-herons, and various waterfowl and shorebirds are also affected.

Northern Shovelers – a common migratory duck in Hawai‘i – are particularly sensitive indicators of botulism because they are efficient filter feeders and thus are most likely to accumulate sufficient toxin to kill. Avian botulism does not affect humans.

NOTE: Although avian botulism Type C does not pose a risk to humans, carcass removal should involve standard hygienic practices including gloves, boots and coveralls.

For more information go to USGS

Please report deaths of waterbirds to the District DOFAW Office on your respective island. On private lands individuals are asked to take the above mentioned recommended wetland management actions to prevent further impacts of this fatal disease.

  • DOFAW Administration Office: 1151 Punchbowl Street, Room 325, Honolulu, Hawai‘i 96813; (808) 587-0166; fax (808) 587-0160.
  • Kaua‘i Branch: 3060 ‘Eiwa Street , Room 306, Lihu‘e , Hawai‘i 96766 ; phone (808) 274-3433; fax (808) 274-3438.
  • O‘ahu Branch: 2135 Makiki Heights Drive , Honolulu , Hawai‘i 96822 ; phone (808) 973-9778; fax (808) 973-9781.
  • Maui Branch (including Moloka‘i, Lana‘i, and Kaho‘olawe): 54 South High Street , Room 101, Wailuku , Hawai‘i 96793; phone (808) 984-8100; fax (808) 984-8111.
  • Hawai‘i Branch : (Hilo Office)19 East Kawili Street , Hilo , Hawaii 96720 ; phone (808) 974-4221; fax (808) 974-4226 ; (Waimea Office) 66-1220A Laiamilo Road, Kamuela Hawai‘i 96743; phone (808) 887-6061; fax (808) 887-6065
  • USGS – National Wildlife Health Center, Honolulu Field Station: Tel. 808 792-9520, 808.792.9521 or 808.792.9523

One Response to “Avian botulism kills 67 birds on Maui, claims over 300 birds on Kauai earlier in the year”

  1. Hawaiiobserver says:

    Botulism huh? How about collision with jets landing and taking off on a new route, or bacterial illness from their emissions?


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